Etiology is a predictor of recurrence after catheter ablation of ventricular arrhythmias in pediatric patients.

BACKGROUND: Ventricular arrhythmias (VAs) are rare in pediatric patients, especially in absence of structural heart disease (SHD). Few data are available regarding the invasive VAs treatment with catheter ablation (CA) in pediatric patients and predictors of outcomes have not been fully investigated. OBJECTIVE: To describe the clinical presentation, procedural characteristics, and outcomes in pediatric patients undergoing CA for VAs. METHODS: Eighty-one consecutive pediatric patients (58 male [72%], 15.5 ± 2.2 years) treated by CA for ventricular tachycardia (VT) or premature ventricular beats (PVBs) were retrospectively evaluated. Study endpoints were VAs recurrence and mortality for any cause. RESULTS: Ninety-five procedures were performed in 81 patients, 52 (55%) PVBs and 43 (45%) VT ablations. During a follow-up of 35.0 months (interquartile range = 13.0-71.0), 14 patients (14.7%) had a VA recurrence: 11 (33.3%) patients treated with CA for VT and 3 (6.2%) patients treated for PVBs (p < .001). One patient (1%) died 26 months after the procedure during an electrical storm. Patients with SHD had higher VAs recurrence rate, as compared with idiopathic VAs (pairwise log-rank p < .001). Patients treated with CA for VT had higher VA recurrence rate, as compared with PVB patients (pairwise log-rank p = .002). At Cox multivariate analysis only SHD was an independent predictor of VAs recurrence (hazard ratio = 5.56, 95% confidence interval = 2.68-11.54, p < .001). CONCLUSION: CA of VAs is effective and safe in a pediatric population. CA of idiopathic and fascicular VAs are associated with lower recurrence rate, than VAs in the setting of SHD.

Long-Term Outcome After Ventricular Tachycardia Ablation in Nonischemic Cardiomyopathy: Late Potential Abolition and VT Noninducibility.

BACKGROUND: In patients with an ischemic cardiomyopathy (ICM), the combination of late potential (LP) abolition and postprocedural ventricular tachycardia (VT) noninducibility is known to be the desirable end point for a successful long-term outcome after VT ablation. We investigated whether LP abolition and VT noninducibilty have a similar impact on the outcomes of patients with non-ICMs (NICM) undergoing VT ablation. METHODS: A total of 403 patients with NICM (523 procedures) who underwent a VT ablation from 2010 to 2016 were included. The procedure end points were the LP abolition (if the LPs were absent, other ablation strategies were undertaken) and the VT noninducibilty. RESULTS: The underlying structural heart disease consisted of dilated cardiomyopathy (DCM, 49%), arrhythmogenic right ventricular dysplasia (ARVD, 17%), postmyocarditis (14%), valvular heart disease (8%), congenital heart disease (2%), hypertrophic cardiomyopathy (2%), and others (5%). The epicardial access was performed in 57% of the patients. At baseline, the LPs were present in 60% of the patients and a VT was either inducible or sustained/incessant in 85% of the cases. At the end of the procedure, the LP abolition was achieved in 79% of the cases and VT noninducibility in 80%. After a multivariable analysis, the combination of LP abolition and VT noninducibilty was independently associated with free survival from VT (hazard ratio, 0.45 [95% CI, 0.29-0.69], P=0.0002) and cardiac death (hazard ratio, 0.38 [95% CI, 0.18-0.74], P=0.005). The benefit of the LP abolition on preventing the VT recurrence in patients with ARVD and postmyocarditis appeared superior to that observed for those with DCM. CONCLUSIONS: In patients with NICM undergoing VT ablation, the strategy of LP abolition and VT noninducibilty were associated with better outcomes in terms of long-term VT recurrences and cardiac survival. Graphic Abstract: A graphic abstract is available for this article.

Fast and safe mapping of ventricular tachycardia in patient with left ventricular assist device.

The characterization of the pathological substrate and/or mapping of the clinical ventricular tachycardia in patients with left ventricular assist device may represent a challenge, due to the risk of entrapment of the intracardiac catheter into the inflow cannula. Hereby, we present the technique of a fast and safe mapping using a 20-poles catheter which allowed the identification of the critical isthmus during ventricular tachycardia.

Phrenic Nerve Limitation During Epicardial Catheter Ablation of Ventricular Tachycardia.

OBJECTIVES: This study sought to investigate the incidence of phrenic nerve (PN) limitation and the utility of displacing the PN with a balloon. BACKGROUND: The PN can limit the epicardial ablation of ventricular tachycardia (VT). METHODS: From 2010 to 2017, 363 patients undergoing VT epicardial ablation at a single center were studied. Before the ablation, we used high output (20-mA) pacing maneuvers to verify the course of the PN. When we observed its capture, we used 1 of 3 different approaches to protect it: 1) non-balloon strategy (nerve-sparing ablation); 2) PN displacement with a small balloon (6 mm × 20 mm); or 3) PN displacement with a large balloon (20 mm × 45 mm). RESULTS: PN capture occurred in 25 patients (7%) at the target ablation site. The most common cause was myocarditis (12 patients [48%]), and the incidence of the PN limitation was significantly higher in myocarditis than in other causes (19% vs. 4%, respectively; p = 0.0002). PN displacement was attempted in 7 patients by using large balloons and in 6 patients with small balloons, resulting in successful PN displacements and complete late potential (LP) abolition in 6 patients (86%) and 3 patients (50%), respectively. Among the 12 patients in whom the non-balloon strategy was used, only 1 patient (8%) achieved LP abolition (compared with the large balloon group; p = 0.002), whereas 3 patients experienced PN paralysis. CONCLUSIONS: The PN limited the epicardial ablation in 7% of patients. Because nerve-sparing ablations often resulted in PN injuries, a possible solution could be to displace the PN with a large balloon, leading to a safer procedure and completion of LP abolition.

Usefulness of Electroanatomical Mapping with Contact Force Monitoring for Accessory Pathways Ablation in Pediatric Population.

The current approach for catheter ablation (CA) of accessory pathways (AP) includes the use of standard catheters under fluoroscopic visualization. We hypothesize that use of contact force (CF) irrigated tip catheters might increase procedural safety in pediatric patients compared to standard irrigated tip catheters, by decreasing the number of radiofrequency (RF) pulses required to obtain AP elimination. Seventy-one pediatric patients (13.7 ± 2.5 years, 45 male) with ventricular pre-excitation were enrolled in the study. CA was performed with a standard irrigated tip catheter up to June 2013 in 41 patients (Group S) and with a CF sensing irrigated tip catheter later on in 30 patients (Group CF). In the Group CF, RF was applied with a minimal CF of 5 g; CF > 35 g was avoided. Group CF procedures required less fluoroscopy (6.8 ± 4.8 min), compared to Group S (12.2 ± 10.8 min, p = 0.007). The number of RF pulses was smaller in Group CF compared to Group S (2.5 ± 2.0 vs 5.5 ± 1.9, p < 0.01). The mean CF during the effective RF pulse was 18 ± 7.7 g, force-time integral was 1040.7 ± 955.9 gs, Ablation Index was 513.0 ± 214.2. The procedure was acutely successful in 70 patients; at 12 months follow-up 2 patients had AP recurrence, one for each group. No major complications were reported. The use of CF irrigated tip catheters was associated with a smaller number of RF pulses and less fluoroscopy, as compared to mapping and ablation with standard irrigated tip catheters.

Late potentials abolition reduces ventricular tachycardia recurrence after ablation especially in higher-risk patients with a chronic total occlusion in an infarct-related artery.

INTRODUCTION: Late potentials (LP) abolition is recognized as an effective strategy for substrate ablation of ventricular tachycardia (VT). The presence of a chronic total occlusion in a coronary artery responsible for a previous myocardial infarction (infarct related artery CTO, IRA-CTO) is emerging as a predictor of ventricular arrhythmias and VT recurrence after ablation. We sought to analyze the effects of LP abolition, focusing on the high-risk subgroup of patients with IRA-CTO. METHODS AND RESULTS: This was a single-center, observational study that screened all patients with prior myocardial infarction and clinical VT, referred for VT ablation at San Raffaele Hospital between 2010 and June 2013. Patients were then included in the study if they had a coronary diagnostic angiography (without revascularization) performed during the index hospitalization. The main endpoint was VT recurrence after ablation. Eighty-four patients formed the population of the study. An IRA-CTO was present in 47 patients (56%) and the presence of an IRA-CTO was a predictor of VT recurrence (HR 3.7, P = 0.005). LP were observed in 51 patients and successfully abolished in 38 cases. LP abolition was associated with lower VT recurrence especially among patients with IRA-CTO (24% vs. 65%, P = 0.005). The presence of an IRA-CTO, in combination with no LP abolition, was the strongest predictor of VT recurrence (HR 4.4, P < 0.001). CONCLUSIONS: Late potentials abolition is an effective strategy for substrate ablation of ventricular tachycardia. The additional reduction of VT recurrence achieved with LP abolition on top of noninducibility is especially significant among high-risk patients with IRA-CTO.

Defining the Outcome of Ventricular Tachycardia Ablation: Timing and Value of Programmed Ventricular Stimulation.

BACKGROUND: Catheter ablation of ventricular tachycardia (VT) is effective to prevent arrhythmia episode-related implantable cardioverter defibrillator shocks. However, recurrences in noninducible patients at programmed ventricular stimulation (PVS) are substantial. METHODS AND RESULTS: From May 2013 to September 2015, 218 PVSs were performed 6 days (5-7) after ablation (186 noninvasive programmed stimulations and 32 invasive PVS) in 210 consecutive patients (ischemic, 48%; median left ventricular ejection fraction, 37%; syncope, 35% with trauma associated 6%), while patients were awake and under ß-blocker therapy. After ablation, implantable cardioverter defibrillators were programmed according to noninvasive programmed stimulations results (class A-noninducible; class B-nondocumented inducible VT; and class C-documented inducible VT), with high and delayed VT detection intervals. Concordance between PVS end procedure and PVS day 6 was 67%. Positive predictive value and negative predictive value were higher for PVS day 6 (53% and 88% versus 43% and 71%). Ischemic and patients with preserved ejection fraction showed the highest negative predictive value (91% and 96%). Among 46 of 174 (26%) noninducible patients at PVS end procedure, but inducible at day 6, 59% had VT recurrence at 1-year follow-up; recurrences were 9% when both studies were noninducible. There were no inappropriate shocks; incidence of syncope was 3%; and none was harmful. The rate of appropriate shocks per patient per month according to noninvasive programmed stimulations results was significantly reduced, comparing the month before and after ablation (class A: 2 [0.75-4] versus 0; class B: 2 [1-4] versus 0; class C: 2 [1-4] versus 0; P<0.001). CONCLUSIONS: PVS at day 6 predicts VT recurrence more accurately allowing to identify patients who might benefit from a redo ablation and addressing implantable cardioverter defibrillator programming.

Characterization of the arrhythmogenic substrate in patients with arrhythmogenic right ventricular cardiomyopathy undergoing ventricular tachycardia ablation.

AIMS: Arrhythmogenic right ventricular (RV) cardiomyopathy (ARVC) is associated with ventricular arrhythmias, even without RV structural disease. We aimed to characterize the RV substrate using electroanatomical mapping and to define outcomes following ventricular tachycardia (VT) ablation in patients with and without RV structural abnormalities. METHODS AND RESULTS: Twenty-nine patients with definite or suspected ARVC undergoing VT ablation were classified as 'electrical' and 'structural' cardiomyopathy based on the absence or presence of major structural criteria. Right ventricular (RV) endocardial and epicardial mapping with assessment of bipolar and unipolar voltages, distribution of late potentials (LPs), and inducible VT morphologies were performed. The endpoints for VT ablation were VT non-inducibility and LP abolition. Fourteen patients were categorized as electrical RV cardiomyopathy and 15 were categorized as structural RV cardiomyopathy. In patients with electrical cardiomyopathy, scar was limited to the epicardial surface (epicardium 13 cm2vs. endocardium 1 cm2, P < 0.05), primarily in the outflow tract, whereas patients with structural disease had greater involvement of the endocardium. During a mean follow-up of 22 ± 11 months, the VT recurrence rate was 27%, with LP abolition being a predictor of VT-free survival (HR 0.075 (0.008-0.661), P = 0.020). There was a trend towards higher recurrence rates in structural RV cardiomyopathy (40%) compared with the electrical cardiomyopathy (15%, P = 0.17). CONCLUSION: The development of RV structural disease in patients with ARVC is associated with extensive epicardial and endocardial scar. Conversely those patients without RV structural disease have identifiable epicardial scar limited to the RV outflow tract. Ventricular tachycardia (VT) ablation in both groups targeting LP abolition is effective in preventing VT recurrence.

Catheter Ablation of Ventricular Tachycardia in Patients With MitraClip Device: Preliminary Findings.

INTRODUCTION: Patients with mitral regurgitation are increasingly treated by percutaneous implantation of a MitraClip device (Abbott Park, IL, USA). We investigate the feasibility and safety of the transmitral catheter route for catheter ablation of ventricular tachycardia (VT) in these patients. METHODS: The mitral valve with the MitraClip in situ was crossed under transesophageal 3-dimensional echocardiographic and fluoroscopic guidance using a steerable sheath for ablation of the left ventricle. RESULTS: Five patients (all males, median age 74.0 ± 16.0 years) who had previously a MitraClip implanted were referred for catheter ablation of VT. The left ventricular ejection fraction was 29.0% ± 24.0%. One patient had both an atrial septal defect and a left atrial appendage occluder device in addition to a MitraClip. The duration between MitraClip implantation and ablation was 1019.0 ± 783.0 days. After transseptal puncture, ablation catheter was successfully steered through the mitral valve with the use of fluoroscopy. A complete high-density map of the substrate in sinus rhythm could be obtained in all patients using multipolar mapping catheters. In 1 patient, mapping was carried out using a mini-basket catheter. Procedural endpoints, noninducibility of all VTs, and abolition of all late potentials were achieved in all patients. Procedure time was 255.0 ± 52.5 minute, fluoroscopy time was 23.0 ± 7.3, and the radiation dose was 61.0 ± 37.5 Gycm2 . No mitral insufficiency or worsening of regurgitation was documented after the procedure. CONCLUSIONS: This is the first report demonstrating the feasibility and safety of VT ablation in patients with a MitraClip device using the anterograde transmitral catheter route.

Left atrial appendage closure: A single center experience and comparison of two contemporary devices.

OBJECTIVES: To compare indications and clinical outcomes of two contemporary left atrial appendage (LAA) percutaneous closure systems in a "real-world" population. BACKGROUND: Percutaneous LAA occlusion is an emerging therapeutic option for stroke prevention in atrial fibrillation. Some questions however remain unanswered, such as the applicability of results of randomized trials to current clinical practice. Moreover, currently available devices have never been directly compared. METHODS: We retrospectively analyzed consecutive patients who underwent LAA closure at San Raffaele Hospital, Milan, Italy between 2009 and 2015. Clinical indications and device selection were left to operators' decision; routine clinical and transesophageal echocardiography (TEE) follow-up was performed. RESULTS: One-hundred and sixty-five patients were included in the study, of which 99 were treated with the Amplatzer Cardiac Plug (ACP) and 66 with the Watchman system. During the follow-up period (median 15 months, interquartile range 6-26 months) five patients died. The incidence of ischemic events was low, with one patient suffering a transient ischemic attack and no episodes recorded of definitive strokes. Twenty-six leaks ≥1 mm were detected (23%); leaks were less common with the ACP and with periprocedural three-dimensional TEE evaluation, but were not found to correlate with clinical events. Clinical outcomes were comparable between the two devices. CONCLUSIONS: Our data show excellent safety and efficacy of LAA closure, irrespectively of the device utilized, in a population at high ischemic and hemorrhagic risk. The use of ACP and 3D-TEE minimized the incidence of residual leaks; however, the clinical relevance of small peri-device flow warrants further investigation. © 2016 Wiley Periodicals, Inc.

Extracorporeal Membrane Oxygenation for Hemodynamic Support of Ventricular Tachycardia Ablation.

BACKGROUND: We report the experience in a cohort of consecutive patients receiving extracorporeal membrane oxygenation during catheter ablation of unstable ventricular tachycardia (VT) at our center. METHODS AND RESULTS: From 2010 to 2015, extracorporeal membrane oxygenation was initiated in 64 patients (average age: 63±15 years; left ventricular ejection fraction in 27±9%; cardiogenic shock in 23%, and electrical storm in 62% of patients) undergoing 74 unstable VT catheter ablation procedures. At least one VT was terminated in 81% of procedures with baseline inducible VT, and VT noninducibility was achieved in 69%. Acute heart failure occurred in 5 patients: 3 underwent emergency heart transplantation, 1 had left ventricular assist device (LVAD) implantation, and 1 patient eventually died because of subsequent mesenteric ischemia. All other patients were discharged alive. After a median follow-up of 21 months (13-28 months), VT recurrence was 33%; overall survival was 56 out of 64 patients (88%). Extracorporeal membrane oxygenation-supported ablation was the bridge to LVAD in 6.9% and to heart transplantation in 3.5% of patients. VT recurrence was related to ablation success (after 180 days of follow up: 19% when VT was noninducible, 42% if nonclinical VT was inducible, 75% when clinical VT was inducible, and 75% in untested patients, P<0.001). Incidence of all-cause death, heart transplantation, and LVAD was independently related to ablation outcome (at 180 days of follow-up: 9% when noninducibility was achieved, 50% in case of inducible VT, and 75% in untested patients, P<0.001). At multivariable analyses, noninducibility (hazard ratio 0.198; P=0.001) and left ventricular ejection fraction (hazard ratio 0.916; P=0.008) correlated with all-cause death, LVAD, and heart transplantation. CONCLUSIONS: Ablation of unstable VTs can be safely supported by extracorporeal membrane oxygenation, which allows rhythm stabilization with low procedure mortality, bridging decompensated patients to permanent LVAD or heart transplantation. Successful ablation is associated with better outcomes than unsuccessful ablation.

The value of the 12-lead electrocardiogram in localizing the scar in non-ischaemic cardiomyopathy.

AIMS: Patients with non-ischaemic cardiomyopathy (NICM) and ventricular tachycardia can be categorized as anteroseptal (AS) or inferolateral (IL) scar sub-types based on imaging and voltage mapping studies. The aim of this study was to correlate the baseline electrocardiogram (ECG) with endo-epicardial voltage maps created during ablation procedures and identify the ECG characteristics that may help to distinguish the scar as AS or IL. METHODS AND RESULTS: We assessed 108 baseline ECGs; 72 patients fulfilled criteria for dilated cardiomyopathy whereas 36 showed minimal structural abnormalities. Based on the unipolar low-voltage distribution, the scar pattern was classified as predominantly AS (n = 59) or IL (n = 49). Three ECG criteria (PR interval < 170 ms or QRS voltage in inferior leads <0.6 mV or a lateral q wave) resulted in 92% sensitivity and 90% specificity for predicting an IL pattern in patients with preserved ejection fraction (EF). The four-step algorithm for dilated cardiomyopathy included a paced ventricular rhythm or PR > 230 ms or QRS > 170 ms or an r ≤ 0.3 mV in V3 having 92 and 81% of sensitivity and specificity, respectively, in predicting AS scar pattern. A significant negative correlation was found between the extension of the endocardial unipolar low voltage area and left ventricular EF (rs = -0.719, P < 0.001). The extent of endocardial AS unipolar low voltage was correlated with PR interval and QRS duration (rs = 0.583 and rs = 0.680, P < 0.001, respectively) and the IL epicardial unipolar low voltage with the mean voltage of the limb leads (rs = -0.639, P < 0.001). CONCLUSION: Baseline ECG features are well correlated with the distribution of unipolar voltage abnormalities in NICM and may help to predict the location of scar in this population.

Right Ventricular Outflow Tract Tachycardia with Structural Abnormalities of the Right Ventricle and Left Ventricular Diverticulum.

A 43-year-old woman presented to the emergency room with a sustained ventricular tachycardia (VT). ECG showed a QRS in left bundle branch block morphology with inferior axis. Echocardiography, ventricular angiography, and cardiac magnetic resonance imaging (CMRI) revealed a normal right ventricle and a left ventricular diverticulum. Electrophysiology studies with epicardial voltage mapping identified a large fibrotic area in the inferolateral layer of the right ventricular wall and a small area of fibrotic tissue at the anterior right ventricular outflow tract. VT ablation was successfully performed with combined epicardial and endocardial approaches.

Left Atrial Appendage: Physiology, Pathology, and Role as a Therapeutic Target.

Atrial fibrillation (AF) is the most common clinically relevant cardiac arrhythmia. AF poses patients at increased risk of thromboembolism, in particular ischemic stroke. The CHADS2 and CHA2DS2-VASc scores are useful in the assessment of thromboembolic risk in nonvalvular AF and are utilized in decision-making about treatment with oral anticoagulation (OAC). However, OAC is underutilized due to poor patient compliance and contraindications, especially major bleedings. The Virchow triad synthesizes the pathogenesis of thrombogenesis in AF: endocardial dysfunction, abnormal blood stasis, and altered hemostasis. This is especially prominent in the left atrial appendage (LAA), where the low flow reaches its minimum. The LAA is the remnant of the embryonic left atrium, with a complex and variable morphology predisposing to stasis, especially during AF. In patients with nonvalvular AF, 90% of thrombi are located in the LAA. So, left atrial appendage occlusion could be an interesting and effective procedure in thromboembolism prevention in AF. After exclusion of LAA as an embolic source, the remaining risk of thromboembolism does not longer justify the use of oral anticoagulants. Various surgical and catheter-based methods have been developed to exclude the LAA. This paper reviews the physiological and pathophysiological role of the LAA and catheter-based methods of LAA exclusion.

Electroanatomical voltage and morphology characteristics in postinfarction patients undergoing ventricular tachycardia ablation: pragmatic approach favoring late potentials abolition.

BACKGROUND: Catheter ablation is an important therapeutic option in postmyocardial infarction patients with ventricular tachycardia (VT). We analyzed the endo-epicardial electroanatomical mapping (EAM) voltage and morphology characteristics, their association with clinical data and their prognostic value in a large cohort of postmyocardial infarction patients. METHODS AND RESULTS: We performed total and segmental analysis of voltage (bipolar dense scar [DS] and low voltage areas, unipolar low voltage and penumbra areas) and morphology characteristics (presence of abnormal late potentials [LPs] and early potentials [EPs]) in 100 postmyocardial infarction patients undergoing electroanatomical mapping-based VT ablation (26 endo-epicardial procedures) from 2010-2012. All patients had unipolar low voltage areas, whereas 18% had no identifiable endocardial bipolar DS areas. Endocardial bipolar DS area >22.5 cm(2) best predicted scar transmurality. Endo-epicardial LPs were recorded in 2/3 patients, more frequently in nonseptal myocardial segments and were abolished in 51%. Endocardial bipolar DS area >7 cm(2) and endocardial bipolar scar density >0.35 predicted epicardial LPs. Isolated LPs are located mainly epicardially and EPs endocardially. As a primary strategy, LPs and VT-mapping ablation occurred in 48%, only VT-mapping ablation in 27%, only LPs ablation in 17%, and EPs ablation in 6%. Endocardial LP abolition was associated with reduced VT recurrence and increased unipolar penumbra area predicted cardiac death. CONCLUSIONS: Endocardial scar extension and density predict scar transmurality and endo-epicardial presence of LPs, although DS is not always identified in postmyocardial infarction patients. LPs, most frequently located in nonseptal myocardial segments, were abolished in 51% resulting in improved outcome.

Impact of a chronic total occlusion in an infarct-related artery on the long-term outcome of ventricular tachycardia ablation.

INTRODUCTION: In patients with a prior myocardial infarction (MI), angiographic predictors of ventricular tachycardia (VT) recurrence after ablation are lacking. Recently, a proarrhythmic effect of a chronic total occlusion (CTO) in a coronary artery has been suggested. METHODS AND RESULTS: A total of 191 patients with prior MI were referred to our Hospital between 2010 and June 2013 for a first ablation of VT. Of these, 84 patients (44%) with stable coronary artery disease that underwent a coronary angiography during the index hospitalization were included in this study. A CTO in an infarct-related artery (IRA-CTO) was present in 47 patients (56%). Patients with and without IRA-CTO did not differ in terms of comorbidities, severity of heart failure, presentation of VT or acute outcome of ablation, that was completely successful in 93% of cases. At electroanatomic mapping, IRA-CTO was associated with greater scar and especially with greater area of border zone (34 cm(2) vs. 19 cm(2) , P = 0.001). Median follow-up was 19 months (IQR 18). At follow-up, patients with IRA-CTO had a significantly higher rate of VT recurrence (47% vs. 16%, P = 0.003). At multivariate analysis, IRA-CTO resulted to be an independent predictor of VT recurrence after ablation (HR 4.05, P = 0.004). CONCLUSIONS: IRA-CTO is an independent predictor of VT recurrence after ablation and identifies a subgroup of patients with high recurrence rate despite a successful procedure. IRA-CTO is associated with greater scars and border zone area; however, this association does not completely justify its proarrhythmic effect.

New diagnostic criteria for identifying left-sided ventricular ectopy using non-contact mapping and virtual unipolar electrogram analysis.

AIMS: To assess the efficacy of non-contact mapping for outflow tract premature ventricular contraction (PVC) and ventricular tachycardia (VT) ablation in patients without structural heart disease and a precordial transition at V3 or later and to determine the diagnostic accuracy of new virtual unipolar electrogram criteria for distinguishing left from right-sided foci using a multi-electrode array positioned within the right ventricular outflow tract. METHODS AND RESULTS: Virtual unipolar electrograms at early activation (EA) and break out (BO) sites in 100 patients (36 left-sided foci) who underwent acutely successful outflow tract ablation were analysed and voltage and timing-based criteria measured. The best performing parameters were then re-assessed in 41 patients (14 left-sided) prospectively. Of the candidate criteria for determining a left from right-sided focus, the voltage at 20 ms after EA (EA-V20) and the time from BO to QRS onset (BO-QRS) were the best discriminators with area under the curve (AUC) values based on receiver operator characteristics (ROCs) of 0.947 (0.905-0.989), P < 0.001, and 0.951 (0.907-0.995), P < 0.001, respectively. These two parameters were subsequently assessed prospectively in a further 41 patients (14 left-sided) using the pre-specified cut-off values of -2 mV for EA-V20 and 10 ms for BO-QRS which demonstrated excellent diagnostic accuracy and sufficient inter-beat and inter-observer reproducibility. CONCLUSIONS: This large single-centre experience demonstrates that a strategy for outflow tract PVC/VT ablation using non-contact mapping allows for excellent success rates. Furthermore, detailed analysis of virtual unipolar electrograms allows accurate and reproducible determination of left from right-sided foci that may be used to guide mapping and ablation.

Electrical storm induced by cardiac resynchronization therapy is determined by pacing on epicardial scar and can be successfully managed by catheter ablation.

BACKGROUND: The mechanism of cardiac resynchronization therapy (CRT)-induced proarrhythmia remains unknown. We postulated that pacing from a left ventricular (LV) lead positioned on epicardial scar can facilitate re-entrant ventricular tachycardia. The aim of this study was to investigate the relationship between CRT-induced proarrhythmia and LV lead location within scar. METHODS AND RESULTS: Twenty-eight epicardial and 63 endocardial maps, obtained from 64 CRT patients undergoing ventricular tachycardia ablation, were analyzed. A positive LV lead/scar relationship, defined as a lead tip positioned on scar/border zone, was determined by overlaying fluoroscopic projections with LV electroanatomical maps. CRT-induced proarrhythmia occurred in 8 patients (12.5%). They all presented early with electrical storm (100% versus 39% of patients with no proarrhythmia; P<0.01), requiring temporary biventricular pacing discontinuation in half of cases. They more frequently presented with heart failure/cardiogenic shock (50% versus 7%; P<0.01), requiring intensive care management. Ventricular tachycardia was re-entrant in all. The LV lead location within epicardial scar was significantly more frequent in the proarrhythmia group (60% versus 9% P=0.03 on epicardial bipolar scar, 80% versus 17% P=0.02 on epicardial unipolar scar, and 80% versus 17% P=0.02 on any-epicardial scar). Ablation was performed within epicardial scar, close to the LV lead, and allowed CRT reactivation in all patients. CONCLUSIONS: CRT-induced proarrhythmia presented early with electrical storm and was associated with an LV lead positioning within epicardial scar. Catheter ablation allowed for resumption of biventricular stimulation in all patients.

Noninducibility and late potential abolition: a novel combined prognostic procedural end point for catheter ablation of postinfarction ventricular tachycardia.

BACKGROUND: Successful late potential (LP) abolition and postprocedural ventricular tachycardia (VT) noninducibility constitute significant end points after catheter ablation for VT. We investigated the prognostic impact of a combined procedural end point of VT noninducibility and LP abolition in a large series of post-myocardial infarction patients with VT. METHODS AND RESULTS: A total of 160 (154 men, 94% with implantable cardioverter defibrillators) consecutive post-myocardial infarction patients undergoing first-time ablation procedures from 2010 to 2012 were included. Of the 159 patients surviving the procedure, 137 (86%) were either inducible or in VT at baseline and 103 (65%) had baseline LP presence, of which 79 (77%) underwent successful LP abolition. The combined end point was assessable in 155 (97%) patients. There were 50 (32%) patients with VT recurrences and 17 (11%) cardiac deaths during follow-up. Patients who fulfilled the combined end point of VT noninducibility and LP abolition compared with inducible patients exhibited a significantly lower incidence of VT recurrence (16.4% versus 47.4%; log-rank P<0.001) and cardiac death (4.1% versus 42.1%; log-rank P<0.001). Among noninducible patients, those with additional LP abolition also had a lower incidence of VT recurrence (16.4% versus 46.0%; log-rank P<0.001). After multivariate analysis, the combined end point of VT noninducibility and LP abolition (hazard ratio, 0.205, P<0.001) was independently associated with VT recurrence and cardiac death (hazard ratio, 0.106; P=0.001). CONCLUSIONS: Achieving a combined catheter ablation procedural end point of VT noninducibility and LP abolition reduces VT recurrence rates to low levels (16%). The overall strategy was associated with a significant impact on cardiac survival.